The present invention is particularly applicable for use in connection with an overhang falsework to minimize the debris which falls over an edge portion of a parallel beam bridge structure and therefore the invention will be described with particular reference to such application. However, the invention has broader applications and may be used in connection with other I-beam structures and other types of construction applications.
It is, of course, well known that debris shields can be used in connection with the construction or repair of a bridge structure to help minimize the amount of debris which can fall from the edges of the bridge structure. While debris shields can take many forms and can be used in connection with any portion of the bridge structure, the overhang falsework of this application is particularly applicable to debris shields which are used on the outermost edges of a bridge structure. These types of debris shields are designed to catch any debris which falls from the bridge deck. In order to accomplish this, debris shields known in the art include both a horizontal portion or base sheet and an upwardly extending portion or side sheet. Turning to the side sheet, it is designed to direct horizontally moving debris from the bridge deck downwardly to the base sheet of the debris shield which ultimately captures the debris. The base and side portions extend longitudinally along the edge of the bridge structure corresponding with the area which is under construction. In view of the potential impact of the debris in certain construction and/or repair circumstances, debris shields are made from shock resistant-material which is typically laminated plywood. While the debris shield is not meant to support the weight of a person, construction supplies or equipment, it must be well supported and securely fastened to the bridge frame structure.
The overhang falseworks are attached to the beams of the bridge frame structure and support the base and side portions of plywood of the debris shield. In general terms, the overhang falseworks include a horizontal member having a connecting arrangement to maintain the falsework relative to the bridge frame. The horizontal or base member also supports the base sheet of the debris shield and an upwardly extending member for supporting the side sheet of the debris shield. While the overhang falsework is only designed to support the debris shield and the corresponding debris, it must be a rigid frame structure and must be securely fastened to the framework of the bridge. Furthermore, in view of the cantilever nature of this type of structure, the horizontal member must be robust enough to support the bending moment of the cantilever forces. Due to the temporary nature of a debris shield and corresponding overhang falsework, the framework of the falsework must also be designed for easy installation and removal from the bridge frame structure. If the frame structure of the overhang falsework is not able to be quickly installed and/or removed, the use of the falsework will be cost prohibitive.
Prior art overhang falseworks are sufficient to support both the base and side sheets of the debris shield. However, they are heavy, difficult to handle, and also create an obstruction below the bridge frame structure. Depending on the application, prior art overhang falseworks are made from at least one wooden member or beam which is either a 2″×6″ or 2″×8″. This wooden beam is secured to the bottom edge of the I-beam bridge frame which also supports the bridge deck. As a result, the overhang falsework can extend between 6 and 10 inches below the bottom edge of the I-beam structure. The wooden beams of prior art falseworks are at least 2″×6″ in cross-sectional configuration since they must extend outwardly from the outermost beam of the bridge frame structure and support the debris shield and the debris at these outward positions. To support the wooden horizontal beam, prior art overhang falseworks also extend inwardly of the outermost I-beam to the I-beam adjacent to the outermost beam. This configuration helps the fastening system of the prior art overhang falsework handle the forces produced by the cantilever falsework design. As a result, the horizontal member of the prior art falsework must be sufficient in length to span two I-beams and to extend outwardly beyond the outer edge of the bridge deck a sufficient amount to provide support for the debris shield. In view of the horizontal member being a wooden 2″×6″ or 2″×8″, this beam structure is very heavy and awkward especially if it is made from side-by-side wooden beams. As a result, prior art falseworks are difficult for a single construction worker to maneuver and install. This is in view of the fact that the overhang falsework is connected to the bottom of the I-beam frame, which requires either scaffolding or the worker being suspended from the overhead bridge structure, etc. Accordingly, the prior art overhang falseworks can be difficult to install. However, the use of a wooden horizontal beam provides a good securing medium for the debris shield in that nails and/or screws can be quickly and easily set into the wooden beam to secure the base sheet of plywood thereto. By utilizing a wooden horizontal beam, the overhang falsework can be reused a number of times to securely hold the debris shield with these fasteners.
The upwardly extending portion of prior art overhang falseworks is also a wooden beam which is permanently attached to the horizontal member by any one of a number of fasteners including nails, screws and/or bolts. As with the horizontal member, the wooden upwardly extending member provides a good medium for either nailing or screwing the side sheet of the debris shield thereto. The upwardly extending member of the overhang falsework is typically a 2″×6″ wooden beam. Permanently connecting the upwardly extending member to the horizontal member creates a rigid joint between the two members. However, it adds further weight to the already heavy horizontal member and the weight is concentrated at the outermost end of the falsework. This configuration makes the falsework unbalanced and even more difficult to maneuver. The resulting L-shaped configuration adds to these difficulties and makes the falsework difficult to store between uses.